The invention herein relates to rotary processors and methods of the general type described in U.S. Pat. Nos. 4,142,805 and 4,194,841. The disclosures of those U.S. Patents are expressly incorporated herein by reference.
The basic rotary processor comprises a rotor defining at least one annular processing channel and a surrounding stationary housing providing a coaxial surface cooperative with each rotor channel to form an enclosed annular processing chamber. The stationary housing has an inlet port to feed material to the annular processing chamber for processing of the material therein, and an outlet port spaced apart from the inlet port to discharge processed material. A stationary channel block member protrudes into the channel and provides a material collecting end wall surface. The channel block member is located in the annular processing chamber near the outlet thereof to obstruct or restrain movement of material within the chamber and to coact with the rotating channel walls to provide relative movement between the material and the channel wall surfaces as they rotate toward the outlet. This distinctive coaction causes melting of the material and permits liquid material in contact with the internal surfaces of the rotating channel to be dragged forward to the collecting channel block for controlled processing and/or discharge.
Many useful commercial embodiments of the basic rotary processor utilize a plurality of processing chambers. The channel of each chamber is defined between facing sidewalls extending inwardly from the rotor surface. The rotor is often comprised of a plurality of spaced-apart discs on a shaft to provide the multiple channels. The stationary housing has an internal cylindrical surface which cooperates with the rotor to close the channels and thereby define the plurality of enclosed annular processing chambers. A plurality of associated channel block members are deployed at a common circumferential position near the outlet of the rotary processor. In one rotary processor described in U.S. Pat. No. 4,389,119, the rotor parts separating the processing chambers are of a reduced diameter to permit material flow between chambers and resultant pressure equalization in the chambers.
In most instances, it has been desirable to provide effective sealing for the individual chambers of a multiple chamber processor in order to prevent unwanted leakage of material therefrom. The unwanted leakage for example can be external leakage from one or both of the end passages of a multiple chamber processor. Also, unwanted leakage can occur internally between adjacent individual annular processing chambers. The leakage of particular concern occurs at the clearance required between the peripheral or outer surface of rotor discs and the adjacent interior coaxial cylindrical surface of the stationary housing, particularly at those portions of the processing chambers where high pressures are generated. This problem has been addressed by providing various sealing means, for instance, those shown in U.S. Pat. No. 4,207,004.
It is also pertinent to an understanding of the invention herein that processing viscous or particulate plastic or polymeric materials often includes the introduction of additives such as carbon black and consequently requires good extensive and good dispersive mixing. Extensive or distributive mixing is characterized by circulation, separation and realigning of the material to achieve overall composition uniformity, or gross uniformity. Dispersive mixing is associated with the reduction in size of a segregated component which has a cohesive nature such as cohesive granular solids, liquid regions with surface tension, as well as vapor or gas bubbles. Dispersive mixing may be characterized as leading to agglomerate break-up, and is generally achieved by providing high shear stress regions, heretofore more readily achieved in blade-type mixing devices. Thus it is desirable to achieve both good extensive and good dispersive mixing in a rotary processor.